1. Field of the Invention
The field of invention relates to a vibration absorbing device for a structure, and, more particularly, to a vibration absorbing device which is installed in a structural member such as a beam or a pillar and a non-structural member such as non-yield strength walls pin-jointed to each other in a structure, or between structural members. More specifically, the field of invention relates to devices which utilize induced rotation of structural members to absorb vibrational energy input to the structure.
2. Description of the Prior Art
Devices presently known for use in absorbing vibrational energy input to a structure upon occurrence of an earthquake or a wind load include elasto-plastic dampers; viscous dampers; oil dampers; oil dampers utilizing viscosity means; and frictional dampers. Among these prior art dampers, the elasto-plastic damper tends to be most commonly used because it is easy to maintain, it is stable during repetitively applied force, and it has great energy absorbability.
The conventional elasto-plastic damper primarily utilizes relative displacement between an upper structure and a lower structure, or relative displacement between any story in a structure and an adjacent story, wherein the elasto-plastic damper absorbs energy by plastic deformation.
An elasto-plastic damper of the type which utilizes relative displacement between upper and lower structure and/or between adjacent stories of a structure must be of sufficient length to span the upper and lower structures, or the adjacent stories. However, the damper body is usually large and requires sufficient space for installation, whereas the space available for such installation is usually limited.
Several examples of prior art elasto-plastic dampers are shown in U.S. Pat. No. 4,901,486. The efficiency of energy absorption in these devices will be influenced by the distance between opposite ends of the elasto-plastic dampers.